Assuming a key repeat rate of 15Hz (a number I admittedly just pulled out of thin air), they would have had to lean on the Tab key for almost exactly 1 week.
The guy ate, slept, possibly got married while his finger was still accidentally holding down that key.
But the seniors on the team pointed to CVS. Not the individual, not the "test" process, not the deploy checks.
Nobody noticed it slow cause everything ran on LAN. Only noticed the issue on 56k